South Korea's Yonhap news agency quoted police as saying that a former singer of a Korean pop women's group was found dead today.
Ko Hara, 28, was found dead in her home south of Seoul, the agency said.
Koo, also known as Hara in other parts of Asia, has strongly criticized online bullying. In June, a month after she was found unconscious at home and taken to hospital, she said depression was difficult to overcome and asked for positive comments on social media.
Kuo began working for the five-girl Kara team in 2008. He was one of the first female bands to help fame Korean pop music and had many fans in Japan, China and other countries.
After her contract with a South Korean agency to run her business, she started singing in Japan and held a concert there this month.
Another pop star, Sully, a member of the FX team and a close friend of Ko, also died of cyberbullying and was found dead in her home last October.